Processing image data for consistent color printing

ABSTRACT

Present systems and methods enable digital color printers to consistently print color output from computer generated image data that includes spot color definitions. Colors that are defined as spot colors can be separated from colors that are defined as combinations of process colors. Accordingly, color corrections can be separately applied to objects that are defined by spot color definitions to provide customized image processing that provides printed color images with improved quality.

TECHNOLOGY

This relates to the printing of color images and more particularly, toprocessing color digital image data to obtain consistent colors in colorimages that are printed on different devices.

BACKGROUND

Generally, color printing is accomplished by creating monochrome subsetsof an image and combining the subsets to obtain the full color image.For example, digital printers typically generate color output bydeveloping each of four electrostatic latent images with a cyan (C),magenta (M), yellow (Y) or black (K) “process color”, then superimposingthe developed images to form the complete image. Production printingpresses generate color hardcopies by generating several printing plates,covering each plate with a different color ink and transferring the inkfrom the separate plates to the hardcopy sheet. Most printing pressesgenerate at least four printing plates, one for providing ink in each ofthe process colors.

Each of the C, M, Y and K colorants absorbs light in a limited spectralregion of the range of visible light; cyan colorant absorbs red light,i.e., prevents light having a wavelength of approximately 650 nm frombeing reflected from the image, magenta colorant absorbs green light(light having a wavelength of approximately 510 nm) and yellow colorantabsorbs blue light (light having a wavelength of approximately 475 nm).Black colorant absorbs all wavelengths of light and can be depositedonto the latent image rather than depositing all three colorants at thesame location. The printable colors are produced by combining thedifferent colorants in various ratios. For example, to generate a blueregion in a hardcopy image, relatively high amounts of colorant will bedeposited onto corresponding locations of the C and M separations, withlittle or no colorant deposited in the corresponding location of the Yseparation. The cyan and magenta colorants will absorb the red and greenlight and thus, only blue light will be reflected from the hardcopysheet and perceived by the viewer.

While printers can usually reproduce a significant number of colors bycombining process colors, such combinations cannot be used to reproduceevery color in the spectral range of visible light. Printing pressestypically provide the additional colors by transferring specially mixed“spot color” inks from printing plates that are formed for that purpose.Digital printers cannot typically add spot colors and thus, the colorgamut for a printer is somewhat limited. The size of the gamut colorsfor a particular printer depends upon several factors, including theprocessing capability of its image processor, the type and quality ofthe marking material and output media used and the viewing environment.

Computer generated color images are printed on both printing presses andcolor printers. The data used to reproduce these images is sometimesprovided in “bit map” form, with color values assigned to the pixels ineach separation to independently control the deposit of C, M, Y or Kmarking materials. Image data is also provided as page descriptions thatdescribe how the printer should mark the page in order to print thedocument. Printer Control Language, produced by Hewlett Packard, PaloAlto, Calif., Advanced Function Presentation, produced by IBM, Armonk,N.Y. PostScript and Portable Document Format (PDF), both produced byAdobe Systems Incorporated of Mountain View, Calif. are examples of wellknown page description languages (PDLs) can generate printable imagedata.

While PDLs generally provide a device-independent way to print images,some aspects of page description are device dependent. For example, PDLsuse a look-up stored on the host computer to define the colors of theobjects in the image. Generally, a look-up table is a database thatassociates color names or other references to the color values thatcontrol the deposit of marking material in the concentrations requiredby a specific printing device. As these color values are determinedbased upon the output characteristics of a specific device, the colorsin the printed output are often incorrect if the file is printed usinganother printer. It would be advantageous to process color image data toprovide consistent colors in images that are printed on any device.

REFERENCES

U.S. Pat. No. 6,690,489 discloses a graphics language interpreterincluding one or more color converters that accept input color valuesand that algorithmically convert such input color values to output colorvalues.

U.S. Pat. No. 6,646,763 discloses methods, systems, and apparatus formapping a nonspectral representation of a target color, such as an inputcolor tuple, to a set of concentration values for a set ofdevice-specific colorants.

U.S. Pat. No. 6,456,395 discloses a method for color separating an imagestored in an encapsulated POSTSCRIPT (EPS) file to be printed to aspot-color printing plate.

U.S. Pat. No. 6,429,950 discloses a method and apparatus that usessimple interpretive programming language commands to generate andregister object characterization information in the form of tagsappended to a plurality of pixel display values stored in the framebuffer of a digital imaging device.

SUMMARY

Aspects of present systems and methods provide a method that includesreceiving an image data file at an electronic device; identifying a spotcolor reference in the image data file; searching a spot colordictionary for a color identifier related to the spot color reference;retrieving from the spot color dictionary, a color vector associatedwith the spot color related color identifier; selecting a color vectoremulation color space based upon a dimension of an identified colorvector; and transforming the color vector to a color value in theselected emulation color space based upon a color vector attribute.

In one aspect, a digital printing device includes a memory thatmaintains a spot color dictionary; an image processor configured toreceive an image data file containing a color definition and generatehalftone color data corresponding to the color definition; and a printengine incorporating a raster output scanner, an imaging member and aplurality of colorants, the print engine being configured to receive thehalftone color data and deposit a plurality of the colorants onto theimaging member as prescribed by the halftone color data, with the imageprocessor being further configured to identify a color referenceembedded in the image data file color definition, to retrieve a colorvector associated with the color reference from the spot colordictionary, to select an emulation color space based upon a color vectordimension, to transform the color vector to a color value in theselected emulation color space based upon a color vector attribute; andto incorporate the selected emulation color space color value into thehalftone color data.

In another aspect, a database includes at least two objects, with atleast one of the at least two objects being a color identifier and atleast one of the at least two objects being a multi-dimensional colorvector.

In yet another aspect, a database includes a plurality of dictionaries,each of which has at least two objects, with at least two of the atleast two objects being a color identifier and an associated amulti-dimensional color vector.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing an exemplary system that can be used tocreate and reproduce digital color images;

FIG. 2 is a detailed illustration showing an example of a color printer;

FIG. 3 is a flow diagram showing one example of how a page descriptionlanguage may specifies and process color specifications in an image datafile;

FIG. 4 is a block diagram showing how separate color corrections can beapplied to objects with colors defined as spot colors and objectsdefined as process color combinations.

FIG. 5 is a block diagram showing how features provided by a pagedescription language can be used to define resources that enable adigital printer to print hardcopy images with consistent colors;

FIG. 6 is a block diagram showing an example of a spot coloridentification procedure for identifying and modifying a spot colorspecification in a page description language file.

FIG. 7 is a flow diagram illustrating an exemplary hashing function.

DETAILED DESCRIPTION

For a general understanding of the present systems and methods,reference is made to the drawings, in which like reference numerals havebeen used throughout. The following term(s) have been used herein todescribe present systems and methods:

As used herein a “color” is the perception of light in a specified rangeof wavelengths as detected by the human eye.

A “colorant” is a material that is added to an object to induce a changein its color.

A “separation” is a medium generated for separately reproducing a singlecolorant.

As used herein a “process color” is one of a finite set of colors thatcan be combined with the others to create the available colors. Processcolors are represented as digital files that include a set of luminanceand chrominance values that are used to reproduce the color.

A “spot color” is a color that is generated using a single colorant.Spot colors are represented as digital files that include a set ofintensity values that represent to the amount of colorant correspondingto the spot color that should be applied to an area of the image.

A “transformation procedure” is a process for converting image data fromapplication space coordinates to device space coordinates.

An “operator” is a word that causes an image processor to carry out apredefined action.

An “object” is a piece of data that is manipulated by a page descriptionlanguage to describe a page.

An “array” is a one-dimensional collection of objects.

A “dictionary” is a table that associates pairs of objects.

A “key” is an object in a dictionary that is associated with a value.When a PDL application refers to a key, the image processor searches theopen dictionaries for the first instance of that key to retrieve theassociated value.

A “name” is a sequence of characters that cannot be interpreted as anumber.

A “resource category” is a collection of named objects that areassociated with a common name. For example, “fonts” and “forms” aredistinct resource categories.

A “color vector” is a multi-dimensional object with an angle and alength that can be used to specify a color value in a color space.

Referring to FIG. 1, present systems and methods may be used to provideprinted color images using a system 10 that includes a host computer 20and a raster output printing device 30 such as, for example, a laserprinter, an ink-jet printer, a digital printing press, etc. Hostcomputer 20 may also be linked to a video monitor 26 and/or to akeyboard 22, a mouse 24 or other input/output device. In the example,shown, host computer 20 has one or more software applications 40 storedin a memory along with a look-up table that a software application 40can use to associate color names or other references to color valuesthat control the deposit of component colorant concentrations for aselected output device.

Software application 40 can be used to create a color image 42 that canbe displayed on video monitor 26 and/or printed at printer 30. In oneaspect, software application 40 generates printable image data using apage description language (PDL), which describes the objects on eachpage in terms of abstract graphical elements. A page descriptionlanguage typically generates an image data file 44 containing commandsthat instruct printer 30 how to deposit marking material onto a page toreproduce objects displayed in color image 42. Unlike the pixel valueassignments provided by a bit map, page descriptions are“device-independent.” That is, they are unrelated to the outputcharacteristics of any particular device. Present systems and methodsare hereinafter described with reference to a software application 40that uses the Adobe PostScript PDL (“PostScript”). It is understood,however, that other types of software applications 40 may be used.

Turning to FIG. 2, image data file 44 is forwarded from host computer 20to printer 30, where an image processor (IP) 32 transforms the pagedescription to halftone data, which is used by a print engine 34 uses todrive the modulated light 33 of a raster output scanner (ROS) 31.Modulated light 33 exposes the surface of a uniformly chargedphotoconductive belt 35 to achieve a set of subtractive latent imagesthat are subsequently developed by depositing cyan (C), magenta (M),yellow (Y) and black (K) “process color” colorants 37 onto the chargeretaining locations of belt 35. The hardcopy color image is then formedby transferring the developed images to a hardcopy sheet in superimposedregistration.

In one aspect, software application 40 defines the colors of the objectsdescribed in image data file 44 using a color definition procedure 100such as that illustrated in FIG. 3. Generally, software application 40selects a color space as shown in block 110 and as shown at block 120,specifies color values that will cause an identified output device 46(not shown) to reproduce the desired colors in the selected color space.In one aspect, software application 40 selects the color values for thenative color space of an output device 46 that is identified by a user.For example, if output device 46 is a video monitor, softwareapplication 40 may select the RGB color space and provide colorspecifications that are defined by three component color values thatrepresent the red (R), green (G) and blue (B) components of visiblelight that the selected monitor will use to display the image. If outputdevice 46 is a color printer, software application may instead selectthe CMYK color space and provide color specifications that are definedby four component color values that the selected printer will use todeposit cyan (C), magenta (M), yellow (Y) and black (K) colorants ontothe hardcopy sheet. The color values for the selected color space areembedded in image data file 44 as shown at block 130.

It may be desirable to forward a single image data file 44 to differenttypes of devices for printing. For example, image data file 44 may beforwarded to a commercial printing press to provide a set of documentsthat are presented to customers and also printed on an office printer toprovide a set of the same documents that are distributed to employees.Accordingly, software applications 40 typically generate image datafiles 44 with color specifications that provide as much detail aspossible, without consideration of whether the information can beprocessed by any particular output device and the determination of howany unusable data will be processed is left to printer 30. For example,a printer 30 that reproduces colors only by combining process colorsmust determine how to process color specifications that identify spotcolors.

Known software applications 40 provide color specifications that include“color names” that are widely used by those who operate different typesof devices to uniquely identify colors. For example, Adobe Systems Inc.,of San Jose, Calif., Corel Corp., of Ottawa, Ontario, Canada, MicrosoftCorp., of Redmond, Wash. and Quark, Inc., of Denver, Colo. each providesoftware applications that use “Pantone Colors,” which are provided byPantone, Inc., Carlstadt, N.J. to facilitate accurate color selection.Software applications 40 also use systems provided by Maibec Industries,Inc., Quebec, Canada (“Truematch”), Colwell Industries, Inc.,Minneapolis, Minn. (“Colorcurve”), Kikuze Solutions Pte. Ltd, Singapore(“Focaltone”) and Toyo Ink Mfg. Co., Tokyo, Japan (“Eco Match”) toidentify colors by name.

Still referring to FIG. 3, printer 30 receives image data file 44 fromhost computer 20 and uses a color rendering procedure 200 to print colorimage 42 in hardcopy format. As shown, color rendering procedure oftenperforms color conversion, illustrated at block 210, to convert thecolor specifications in image data file 44 to the native color space ofprinter 30. For example, if software application 40 generates an imagedata file 44 for a video output device 46, image data file 44 maycontain RGB data that is converted to CMYK format at block 210. Colorrendering procedure also includes gamma correction, shown at block 220,which corrects distortions that are introduced by printer 30,halftoning, illustrated at block 230, which converts the image data tothe binary format required by printer 30 and scan conversion, shown atblock 240, which places the markings onto the output sheet.

During halftoning (block 230), IP 32 typically references a look-uptable stored on a host computer that is linked to printer 30, ratherthan the look-up table associated with output device 46, which is storedon host computer 20. If the color name-color value associations in thelook-up table used by printer 30 differ from those contained in thelook-up table of output device 46, the hardcopy image provided byprinter 30 often displays the wrong colors.

Output device 46 typically generates an image data file 44 that providecolor specifications that identify process color combinations at block210 (or with specifications that provide color values that can easily beconverted to process color combinations, e.g., RGB data). Quite often,output device 46 also provides at least some color specifications thatidentify spot colors. Color definitions for spot colors usually providea device-dependent or CIE-based color space along with the color valuesthat output device 46 can use to reproduce the color.

For example, a software application 40 that uses PostScript may define acolor that can be reproduced as a combination of process colors byselecting a color space and providing a color vector for reproducing thecolor in the selected color space. The following text string is anexample of a PostScript array that can be used to select the CMYK colorspace: “[/DeviceCMYK] setcolorspace.” A command such as this wouldtypically be followed by a string such as: “[/value-c: value-m: value-y:value-k] setcolor,” which provides the C, M, Y and K component colorvalues used by output device 46 to reproduce the color in the CMYK colorspace.

In contrast, software application 40 would typically define a spot colorusing the following text: “[/Separation RefName alternativeSpacetintTransform] setcolorspace,” followed by the text “[/value-s]setcolor,” wherein value-s is a single tint component between 0.0 and1.0. The term “alternativeSpace” represents an alternative color spacefor reproducing the color and the term “tintTransform” identifies aprocedure used to convert “value-s” to the alternate color space. Aprinter that reproduces colors as process color combinations can respondto the following syntax by emulating the spot color identified as“RefName Red 081 D”:

[ /Separation (RefName Red 081D) /DeviceCMYK { dup 0.00 mul exch dup0.87 mul exch dup 0.91 mul exch dup 0.00 mul exch pop } ] setcolorspace

In other words, printer 30 can completely withhold colorant from thespecified pixels in the cyan separation, deposit 87% of the maximumavailable colorant at the same pixels in the magenta separation, deposit91% of the maximum available colorant at the same pixels in the yellowseparation and completely withhold colorant from the same pixel in theblack separation to emulate the color RefName Red 081 D in the CMYKcolor space. The term “RefName” is a generic term for a color name orother reference of the type commonly used in commercially availablecolor matching systems. For example, the color names “Cosmos Blue 2712,”“Lionogen Violet VC6100,” “Lionol Green 6Y-501” and “Rubine RLD” areknown as unique identifiers for the associated colors.

The differences in the way software applications 40 define process andspot colors can be used to identify the color definitions for spotcolors and significantly, to modify those definitions to obtain accuratecolor reproduction on any digital printer. For example, the definitionfor a spot color in a PostScript command can be identified by a requestfor an emulated color space and a customized operation can be defined tomodify the spot color request to satisfy a specific requirement of theapplication.

Digital printers that are currently available offer options foremulating certain printing conditions. For example, Xerox Phaser®printers provide color correction options that simulate the print ofprinting presses that meet the SWOP Press (Specification for Web OffsetPublications) Press, SNAP Press (Specifications for Non-Heat AdvertisingPrinting) Press, Commercial Press (Four-Color U.S.) and Euroscale Pressstandards, which enables users to preview their images before they areactually printed on the selected device. When such options are selected,a predefined color correction is automatically applied to the colorsdefined in image data file 44.

Since spot color definitions provide their own color transformationcommands, many color printers are unable to print spot colors accuratelywhen an automatic color correction has been selected. More specifically,if one of the printing press emulations has been selected, the colorcorrection that simulates the printing press overrides the tintTransformprocedure of the spot color specification.

In one aspect, since objects in image data file 44 with colors definedby process colors can be distinguished from those defined by spotcolors, objects with spot color definitions can be directed to a colorcorrection path that is specially created to process spot colors for theselected printing press and objects with process color definitions canbe directed to the standard printing press color correction.

Turning to FIG. 4, present systems and methods use a spot coloridentification procedure 310 to isolate objects with colors that aredefined as spot colors. When printer 30 receives an image data file 44,IP 32 searches for spot color definitions as shown in block 311. Forexample, if PostScript is used, IP 32 determines that a spot color ispresent when a “/Separation” command, which requests a color space fordefining spot colors, is found in image data file 44. Color processingcan then be applied to each object based upon its color definition type.

In one aspect, to provide a printed data that emulates the outputprovided by a selected device, colors that define objects as spot colorsmay be subjected to a spot color correction process as shown at block313, which differs from a process color correction process that isapplied to colors that define objects as process color definitions asshown at block 315. IP 32 performs halftoning when color data has beenprocessed for all of the objects in the image as indicated in block 318.

While the color names in spot color requests are device-independent, thealternate color space and transformation procedure commands are definedbased upon the output characteristics of output device 46. Accordingly,the colors output by printer 30 will be incorrect if the alternate colorspace and transformation procedure were selected for a different targetprinter.

Turning to FIG. 5, present systems and methods add custom features to acontrol program IP 32 uses to interpret an image data file 44 generatedby a page description language program. In one aspect, present systemsand methods provide a “SpotColor Resource Category” (SRC) 60 thatincludes a plurality of Spot Color Dictionaries (SCDs) 50. SCDs 50contain a plurality of Color Identifiers (CIDs) 52, each of which is akey associated with a Spot Color Vector (SCV) 54. CIDs 52 identify thecolor names that may be embedded in an image data file 44 by a softwareapplication 40. A CID 52 may relate to color names that are provided byPantone, Truematch, Colorcurve, Focaltone and other known color matchingsystems.

In one aspect, SCV 54 is a multi-dimensional color vector that definesan output color. In one aspect, SCV 54 is a three dimensional value thatrepresents the red, green and blue components of visible light that arecombined to produce a specified color. In another aspect, SCV 54 is afour dimensional value that represents the cyan, magenta, yellow andblack colorant concentrations that create a printed image. In oneaspect, SCV 54 is stored in a memory linked to printer 30.

Turning to FIG. 6, present systems and methods provide a spot colorcorrection procedure 320 that modifies the color specifications forobjects with colors that are defined as spot colors. When a spot colordefinition is encountered in image data file 44, IP 32 initiates asearch through the SRC 60 hierarchy to obtain the color data that can beused to accurately reproduce the requested color. In one aspect, whenimage data file 44 is delivered to printer 30 as shown at block 321, IP32 begins searching image data file 44 for a spot color name as shown inblock 322. If no spot color name is found, IP 32 concludes that thecolor specification is for a process color combination and the color isreproduced normally as shown at block 323. However, if IP 32 locatesspot color name, the alternateSpace parameter in the color definition isreplaced with /DeviceRGB if SCV 54 is a three dimensional value or with/Device CMYK if SCV 54 is a four-dimensional value. IP 32 will thenprovide either an RGB color value or a CMYK color value to replace thetintTransform parameter by converting SCV 54 to the identifiedalternateSpace.

Since CIDs 52 are not linked to any particular color matching system,present systems and methods need not process any portion of image datafile 44 that is relates only to a specified color matching system. Thus,in one aspect, present systems and methods may optionally extract CID 52from the data image data file 44, or delete (or modify, ignore, bypass,etc.) references to color matching information from image data file 44at block 324. Accordingly, present systems and methods can be used withcolors provided by multiple color reference systems. It is understood,however, that present systems and methods can be used without removinginformation for specific color reference systems.

In one aspect, a hashing function may be applied to image data file 44to remove a predetermined number of characters from a predeterminedposition of image data file 44. For example, the hashing function maydelete the first five characters of the text string that incorporatesCID 52 or leave the first six characters and delete the next three, etc.

In one aspect, a “hashing function” may be used to map color names thatare widely used to CIDs 52 or to references that are proprietary or arenot otherwise available to the public. Present systems an methods maythen search SCD 50 for CID 52, rather than a spot color name. As shownin FIG. 7, an algorithmic mapping may be applied to the color definitionidentified in image data file 44 before IP 32 initiates its search ofSCD 50. Accordingly, the entire gamut of printer 30 can be used toreproduce colors without requiring the presence of the exact referencesthat are used by all of the available color matching systems in look-uptable maintained by printer 30 to reproduce widely used colors.

For example, an algorithm may convert the first X characters of thecolor definition string to the first Y characters of a CID 52. It isnoted that the memory required is likely to be reduced if X>Y. However,present systems and methods may be used if X=Y or X<Y. In one aspect,mapping may take the form of an exclusive or (XOR) operation performedon the data. The remaining characters of CID 52 may be provided bysimply copying some portion of the remaining characters of the colordefinition string to an identified portion of CID 52. It is understoodthat present systems and methods may also search SCD 50 for an entirespot color name, or search for a CID 52 that is obtained withoutapplying an algorithm such as that described and that they may be usedwith a CID 52 obtained without using any algorithm or mathematicalfunction.

Color identification procedure 310 also includes searching the defaultSCD 50 at block 325 to locate the identified CID 52. In one aspect, auser may design a user custom SCD 50 with definitions for customizedcolors, such as those used in a logo. In another aspect, SCDs 50 may beprovided with the color names provided by one or more color matchingsystems that provide spot colors. In another aspect, printer 30 maymaintain a SCD 50 to provide its own color definitions. In one aspect,color identification procedure may, for example, first search usercustom SCD 50 for an identified color name, then one or more colormatching systems and finally search the SCD 50 maintained by printer 30only if the spot color has not been identified.

When the CID 52 (or spot color) identified by image data file 44 islocated, IP 32 retrieves the associated SCV 54 and uses it to select analternative color space as indicated at block 326. More specifically, ifSCV 54 is a three dimensional vector the “alternateSpace” information isreplaced with /DeviceRGB and if SCV 54 is a four dimensional vector the“alternateSpace” information is replaced with /DeviceCMYK. SCV 54 isalso used at block 327 to replace the tintTransform portion of the datain image data file 44 with the color values that reproduce the color inthe selected color space as shown at block 327.

While present systems and methods are described as being used withsoftware applications that have been provided by the aforementionedentities, that use a PDL to generate image data files and that and useproprietary color naming systems, it is understood that present systemsand methods could be used with other software applications, thatgenerate image data in other was and that present systems and methodsmay be used with any references that are embedded in image data files 44to define colors. It is also understood that the commands provided by animage data file 44 may be used by output devices other than printers.

It will be appreciated that various of the above-disclosed and otherfeatures and functions, or alternatives thereof, may be desirablycombined into many other different systems or applications. Also thatvarious presently unforeseen or unanticipated alternatives,modifications, variations or improvements therein may be subsequentlymade by those skilled in the art which are also intended to beencompassed by the following claims.

1. A digital printing device, comprising: a memory that maintains a spotcolor dictionary; an image processor configured to receive an image datafile containing a color definition and generate halftone color datacorresponding to said color definition; and a print engine incorporatinga raster output scanner, an imaging member and a plurality of colorants,said print engine being configured to receive said halftone color dataand deposit a plurality of said colorants onto said imaging member asprescribed by said halftone color data, with said image processor beingfurther configured to: identify a color reference embedded in said imagedata file color definition, retrieve a color vector associated with saidcolor reference from said spot color dictionary, select an emulationcolor space based upon a color vector dimension, transform said colorvector to a color value in said selected emulation color space basedupon a color vector attribute; and incorporate said selected emulationcolor space color value into said halftone color data.
 2. A digitalprinting device as claimed in claim 1, wherein said image processor isfurther configured to retrieve a color vector from said spot colordictionary that has a first dimension representing a red component ofvisible light reflected from an image, a second dimension representing ablue component of visible light reflected from an image and a thirddimension representing a red green component of visible light reflectedfrom an image.
 3. A digital printing system as claimed in claim 1wherein said image processor is further configured to retrieve a colorvector from said spot color dictionary that has a first dimensionrepresenting a concentration of cyan colorant to be deposited in animage, a second dimension representing a concentration of magentacolorant to be deposited in an image and a third dimension representinga concentration of yellow colorant to be deposited in an image.
 4. Adigital printing system as claimed in claim 1, wherein said imageprocessor is further configured to retrieve a color vector from saidspot color dictionary that has a fourth dimension representing aconcentration of black colorant to be deposited in an image.
 5. Amethod, comprising: receiving an image data file at an electronicdevice; identifying a spot color reference in said image data file;searching a spot color dictionary for a color identifier related to saidspot color reference; retrieving from said spot color dictionary, acolor vector associated with said spot color related color identifier;selecting a color vector emulation color space based upon a dimension ofan identified color vector; and transforming said color vector to acolor value in said selected emulation color space based upon a colorvector attribute.
 6. A method as claimed in claim 5 further comprising:extracting said color identifier from said spot color reference; andusing said color identifier to retrieve said color vector.
 7. A methodas claimed in claim 6 further comprising searching a plurality of spotcolor dictionaries for said spot color reference related coloridentifier until said color identifier is located.
 8. A method asclaimed in claim 7 further comprising searching a user custom spot colordictionary for said color identifier.
 9. A method as claimed in claim 7further comprising searching a color matching system spot colordictionary spot color dictionary for said color identifier.
 10. A methodas claimed in claim 5 wherein said electronic device is a digitalprinter and said spot color dictionary is stored in a local memorylinked to said digital printer.